CO-29CO group · Administrative

CO-29 denial code: the timely filing limit has expired

A CO-29 is procedural, not clinical — which is exactly why it's winnable when you have proof you filed on time. The whole appeal turns on documentation.

CO-29 means the claim was received after the payer's timely-filing deadline. It is one of the most appealable administrative denials, because the dispute is purely about whether you filed in time — and that is provable. The strongest proof is an electronic acceptance record (a 277CA or clearinghouse acknowledgment) tying the claim to a date inside the window.

What CO-29 means

Every payer sets a window from the date of service in which a claim must arrive. Miss it and the claim is administratively denied as CO-29. Windows vary widely by payer and plan type — and the deadline that applies depends on the plan type, not only the payer.

Why CO-29 fires

  • The claim genuinely arrived after the deadline.
  • An earlier submission was rejected at the clearinghouse and never reached the payer (a rejection is not an accepted claim).
  • The claim bounced between primary and secondary payers and the COB clock ran out.
  • The payer has no record of an on-time submission you believe you sent.

Is CO-29 worth appealing?

Sometimes worth appealing

Highly appealable when you can prove timely submission. The case is built on the acceptance trail: a 277CA accepted-claim acknowledgment or clearinghouse report dated within the window beats a screenshot every time. Where the delay was caused by the payer (wrong COB, incorrect denial, or eligibility error), cite that as good cause.

How to resolve or appeal CO-29

  1. 1

    Pull the acceptance proof

    Find the 277CA or clearinghouse acknowledgment showing the claim was accepted within the filing window. This is the single most important attachment.

  2. 2

    Document any payer-caused delay

    If the claim was first sent to the wrong payer due to incorrect eligibility/COB, or was wrongly denied and reworked, show that timeline as good cause for the late receipt.

  3. 3

    Cite the correct deadline for the plan type

    Filing limits depend on plan type. For Medicare fee-for-service the claim-filing limit is set in federal regulation; commercial and Medicaid windows differ. State the governing window, not a generic one.

CO-29 — frequently asked

What's the best proof of timely filing?
An electronic acceptance record — a 277CA accepted-claim acknowledgment or a clearinghouse acceptance report dated inside the filing window. A printout of your billing screen is weak by comparison.
Does a clearinghouse rejection count as filing on time?
No. A rejection means the claim never reached the payer. Only an accepted/acknowledged submission counts as timely.

Related guides

Read a full sample CO-29 appeal letterCO-22 · Coordination of benefitsCO-109 · EligibilityCO-16 · Administrative

Sources

Reason-code meanings are paraphrased from the X12 Claim Adjustment Reason Code list for plain-language reference; they are not reproduced verbatim. This is general information, not legal, coding, or medical advice — always confirm against the payer's remittance and policy.

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